This invention is applicable to various types of light powdery granule treating systems and especially, efficiently applicable to, for example, a system of the type for condensing lupulins of hop. Therefore, the present invention will be described hereinafter in conjunction with such a type of treating system.
This type of treating system and method have already been disclosed in U.S. Pat. Nos. 4,051,771 and 4,053,653. The known system is partially modified and illustrated in FIG. 1.
To describe the system briefly, a supply conduit 1 comprises a magnetic separator having a hopper and magnets mounted on the outer surface of the hopper. Lupulins supplied to this supply conduit are fed to a conveying pipe 51 via a treating means 2 comprising a screw feeder and conveyed by wind power through the pipe 51 to a storage tank 3. Part of the conveying air reaching an air pipe 52 via an upper portion of the storage tank 3 is drawn by an air blower 16 into a cooler 15 and cooled thereat. Eventually, the cooled air circulates to the conveying pipe 51. Eventually, the cooled air circulates to the conveying pipe 51. Consequently, the hops are normally cooled to -5.degree. C. or less and water contained therein is frozen. The remainder of the conveying air discharged from the upper portion of the storage tank 3 is sucked by a suction pump 18 so as to be drawn into an air cooler 17 within which it is cooled, and eventually circulates to the storage tank 3. A stirring blade 25 is disposed at the bottom of the storage tank 3 which is connected with a supply means 26 comprising a screw feeder, so that the hops cooled to about -20.degree. C. by the cooling wind are stirred by the blade 25 and conveyed by the supply means 26 so as to be fed via a supply conduit 27 to a treating means 4 comprising a crusher.
The hops crushed at the treating means 4 are conveyed through a conveying pipe 53 under the application of wind power to a first cyclone 12 where the conveying air and the hops are separated from each other. The air is fed to a first bag filter 14 via an air pipe 54 and drawn into an air cooler 19 by the actio of a first turbofan 20. Part of the air circulates to the conveying pipe 53 via an air pipe 55. Meanwhile, the separated hops are conveyed, through a supply conduit 22 with an air locker 13, to a treating means 5 comprising a shaking sieve.
The treating means 5 has a sieve which consists of several stages of different meshes, so that minus sieve or undersize granules are fed to a receiver 7, plus sieve or oversize granules are fed to a crusher 28 via a supply conduit 23, and air containing the remaining powdery granules is fed via an air pipe 56 to a second bag filter 29. Eventually, the air removed of the powdery granules is drawn up by the action of a second turbofan 21 toward the atmosphere and the granules precipitate so as to be discharged to the outside.
The oversize granules are crushed by the crusher 28 in the same manner as by the treating means 4, and resulting granules are fed via a conveying pipe 57 to a second cyclone 30 where air is separated from the granules or hops. The air is discharged to the air pipe 54 via an air pipe 58, and the hops are conveyed, through a supply conduit 32 with an air locker 31, to a rotary sieve 6. Minus sieve granules are discharged to a receiver 33, and plus sieve granules, put together, are discharged to an outlet pipe 34 with an air locker 8. The plus sieve granules are crushed by air supplied from an air blower 9, fed to a storage tank 10 for waste, and exhausted therefrom through a screw conveyor 35 to a waste packer 11.
In the above system, a crusher 38 is disposed, though not disclosed in the aforementioned U.S. Patent, before the supply conduit 1 as shown in FIG. 2. The crusher 38 has a hammer 37 which is rotated by a motor, not shown, to crush the raw hops. The thus crushed hops are supplied to the supply conduit 1 equipped with magnets 41 through a bucket conveyor 40 driven by a motor 39.
The treating system described so far fulfils its excellent function as detailed in the aforementioned U.S. Patent but it still faces difficulties that clogging of the powdery granules occurs in the line system, particularly, in the supply conduits 1 and 27 and air cooler 17 connected to the treating means 2, 4 and 5, respectively. When a predetermined operational condition is set in respect of the raw hops used as a material to be treated, the clogging will occur if the hop change in quality, or the clogging will occur dependent on the weather condition during operation and the condition of the system even if the hops remain unchanged. The clogging thus caused leads to troubles of the system and the occurrence of the clogging must be prevented. To this end, the setting of the operational conditions must be revised frequently in consideration of the above conditional factors but adjusting operations for this purpose are difficult to achieve and time consuming, thus deteriorating efficiency and the quality of the material to be treated. In addition, once the clogging occurs, the operation of the system must be stopped and components of the system subject to the clogging must be disassembled for removal of the clogging.
Under the circumstances, the inventors of the present invention have studied measures for elimination of the above disadvantages and searched for the cause of the occurrence of the clogging to find a phenomenon to be described below with reference to FIG. 2. When the amount of hops "a" supplied to the supply conduit 1 through the bucket conveyor 40 is balanced with the amount of hops discharged to the outside through the treating means 2, the hops "a" form a thin massive flow, as indicated by solid line, which slips down within the supply conduit 1. But, as the supply amount increases to exceed the outlet amount, the hops begin to stagnate gradually within the supply conduit 1. When the stagnant hops form a thick massive flow which exceeds a thickness as indicated by chained line, clogging of the hops or powdery granules takes place. To eliminate this adverse phenomenon, it may be conceived that the supply amount is always held in excess of the outlet amount by making the treating means 2 have a treating capacity which is greater than that of the conveyor 40. This expedient is however fruitless because the treating means 2 is required to have a capacity which is greater than that normally required and which becomes therefore surplus during the normal operation. Such an inconvenience may be overcome or avoided by decreasing the supply amount in proportion to a decrease in the outlet amount.